The invention relates to an electric automatic circuit breaker including a mechanic spring mechanism for the actuation of circuit breaker contact means. The contact means are arranged in an arc chamber in front of the facing end of a quenching sheet metal stack. The contact means are freely releasable either manually, electromagnetically or by thermo-electric means. The term "releasable" as used herein means the breaking or opening of a contact. Such circuit breakers are employed especially in connection with small installation circuits. It is one purpose of such circuit breakers to reduce as much as possible the mechanic circuit breaking delay in response to a short circuit or in response to a line overloading which will cause the circuit breaker release with sufficient speed to induce an arc voltage in the short circuit loop. Such arc voltage should be as high as possible for limiting the short circuit current in its size and effect.
Another purpose of these automatic circuit breakers is to quickly and completely quench the arc, which is generated across the electric contact break distance during the contact separation under load. Such arc carries a rather strong current, the rapid and complete quenching of which is essential if the automatic circuit breaker shall remain operational. Conventionally, this is achieved substantially by permitting the arc column emanating from the contact device of the circuit breaker to impinge with a high propagating speed upon the front face of a quenching sheet metal stack, whereby the arc column is divided into a number of partial arcs. A sufficient cooling and de-ionization of the arc gases is accomplished in this manner. These gases simultaneously escape through pressure equalization channels and the like, whereby the gases contribute to an instantaneous quenching of the circuit opening arc.
Prior art devices of this type employ for this purpose exclusively a contact device arranged in the space adjacent to or in front of the quenching sheet metal stack. A contact member constructed either as a bridge contact or as a pivoting contact is arranged to lift off from a fixed contact arranged opposite the movable contact member for opening the circuit across the contact break distance extending in parallel to the individual sheet metal strips of the quenching stack. In order to facilitate the entering of the resulting arc into the quenching sheet metal stack, it is necessary to directly extend the fixed contact by means of an additional guide rail to a guide plate of the quenching stack. Further, the movable contact member must be provided with a special run-off prong for the arc. In such an arrangement it is unavoidable that the arc running off the contact device must jump in any event from the movable contact member to the respective guide plate of the quenching stack in order to enter into the quenching stack. Such jumping not only impedes a continuous run-off of the switching arc it also opposes the arc stability and slows down the propagation speed of the arc whereby the entire arc quenching is substantially prolonged.
Furthermore, prior art automatic circuit breaker constructions of the mentioned type employ exclusively relatively complicated as well as bulky switching means, whereby it becomes impossible to reduce the available dimensions in the range of higher arc interrupting ratings. This is especially disadvantageous, if one intends to house as many automatic circuit breakers as possible in the usually limited space for this purpose, for more selectively monitoring the circuits of an installation.